1. Field of the Invention
The present invention relates to a process of forming an amorphous alloy material having excellent strength and corrosion resistance.
2. Description of the Prior Art
Since a high cooling rate is required for the production of amorphous alloys in a conventional manner, liquid quenching, gas atomization or the like has been used to obtain amorphous alloys such as iron-based or nickel-based amorphous alloys in the form of ribbons or powder. Further, wire-like amorphous alloys have also been obtained by in-rotating-water spinning or the like. Making use of their characteristic properties, they have found wide-spread commercial utility as magnetic materials, high-strength materials, corrosion-resistant materials, etc.
To form these alloys into a plate-like configuration, it is however necessary to use extrusion, rolling and the like forming processes, either singly or in combination. The materials described above however have high strength so that it is difficult to apply these forming processes. Plate-like amorphous materials, as blanks for forming work, cannot be obtained with ease. It is therefore the current situation that there is practically no product formed from a plate-like amorphous material. On the other hand, a certain type of crystalline materials shows superplasticity when their grain sizes are precisely controlled. Forming processes making use of this phenomenon are applied to plate-like materials, whereby products of a complex configuration are manufactured. This superplastic working is however accompanied by the drawback that the working speed is very low and complex steps are required for the control of the grain size.
As has been described above, conventional amorphous alloy materials can be formed by direct quenching such as liquid quenching, as atomization or in-rotating-water spinning. It is difficult, however, to directly produce plate-like amorphous materials from such alloy materials and by such processes.
From alloys capable of showing glass transition, on the other hand, it is possible to produce plate-like amorphous materials by applying extrusion, rolling and the like, either singly or in combination, to amorphous alloys, which have been obtained in the form of a ribbon or powder, as, inter alia, in Japanese Patent Laid-Open Nos. 3-10041, 3-36243 and 3-158446. Although production processes relying upon one or more of these working techniques are excellent, the working requires many steps, leading to the existence of room for improvements, from an economical standpoint.
The present inventors have already discovered that the alloys disclosed in the above applications, the alloys being capable of showing glass transition, can be formed into amorphous bulk materials by direct casting or the like. An application for patent has already been filed based on this finding (Patent Application No. 2-49491). It has now been found that a plate-like formed product can be obtained economically and with ease by forming such a bulk material (plate material) in a temperature range of from glass transition temperature (Tg) to crystallization temperature (Tx), leading to the completion of this invention.